GRE Subject Test: Physics : Fundamental Properties

Study concepts, example questions & explanations for GRE Subject Test: Physics

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Example Questions

Example Question #1 : Fundamental Properties

A particle traveling through glass (index of refraction 1.33) emits Cherenkov radiation. Which of the following is a possible speed of the particle?

Possible Answers:

Correct answer:

Explanation:

Cherenkov radiation is emitted by a particle traveling faster than the phase velocity of light in that medium. Because , the phase velocity of light in the glass is:

This is the minimum velocity of a particle to be emitting Cherenkov radiation in glass. This eliminates all answers except  and The latter is impossible because it is greater than the speed of light in a vacuum, therefore the answer is .

Example Question #2 : Fundamental Properties

A monochromatic beam of  light travels through a material with a phase velocity of . What is the refractive index of the material?

Possible Answers:

Correct answer:

Explanation:

The phase velocity of light through a medium with refractive index  is given by:

Solving this for  and substituting our given value of :

All GRE Subject Test: Physics Resources

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